Physical and Chemical Changes Worksheet - Cobb Learning - Free Printable

Let's solve the problem step by step based on the worksheet titled "Physical and Chemical Properties and Changes."

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🔹 Part 1: Identify as Physical (P) or Chemical (C) Property

We are given definitions:

- Physical Property: Observed with senses, determined without destroying matter.
- Chemical Property: How a substance reacts with something else; matter changes into a new substance.

Now, classify each:

| # | Property | Type (P/C) | Explanation |
|---|--------|------------|-----------|
| 1. blue color | P | Color is observed visually, no change in substance |
| 2. density | P | Measured without changing the substance |
| 3. flammability (burns) | C | Involves combustion → new substances formed |
| 4. solubility (dissolves) | P | Dissolving doesn't change chemical identity (e.g., sugar in water) |
| 5. reacts with acid | C | Reaction produces new substances |
| 6. supports combustion | C | Indicates ability to react with oxygen |
| 7. sour taste | P | Taste is a sensory property, not destructive |
| 8. melting point | P | Temperature at which solid becomes liquid — no new substance |
| 9. reacts with water | C | Chemical reaction occurs (e.g., Na + H₂O → H₂ + NaOH) |
| 10. hardness | P | Physical characteristic |
| 11. boiling point | P | Phase change without altering composition |
| 12. luster | P | Visual appearance of surface |
| 13. odor | P | Smell is physical observation |
| 14. reacts with air | C | Oxidation (e.g., rusting) creates new substances |

✔ Answers:
1. P
2. P
3. C
4. P
5. C
6. C
7. P
8. P
9. C
10. P
11. P
12. P
13. P
14. C

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🔹 Part 2: Identify as Physical (P) or Chemical (C) Change

Definitions:

- Physical Change: Change in size, shape, or state; no new substance formed.
- Chemical Change: New substance is formed; properties change.

| # | Change | Type (P/C) | Explanation |
|---|-------|------------|-----------|
| 1. NaCl (Table Salt) dissolves in water | P | Dissolution is physical; salt can be recovered by evaporation |
| 2. Ag (Silver) tarnishes | C | Silver reacts with sulfur → silver sulfide (black tarnish) |
| 3. An apple is cut | P | Only shape changed; no new substance |
| 4. Heat changes H₂O to steam | P | Phase change (liquid → gas), same molecule (H₂O) |
| 5. Baking soda reacts to vinegar | C | Produces CO₂ gas → new substances formed |
| 6. Fe (Iron) rusts | C | Iron oxidizes → iron oxide (rust), new compound |
| 7. Alcohol evaporates | P | Evaporation is physical state change |
| 8. Ice melts | P | Solid → liquid, still H₂O |
| 9. Milk sours | C | Bacteria cause fermentation → lactic acid produced |
| 10. Sugar dissolves in water | P | No chemical reaction; sugar molecules remain intact |
| 11. Wood rots | C | Decomposition by fungi/microbes → new substances |
| 12. Pancakes cook | C | Maillard reaction, browning, proteins denature → new compounds |
| 13. Grass grows | C | Photosynthesis → new organic molecules made |
| 14. A tire is inflated | P | Air is added; no chemical change |
| 15. Food is digested | C | Enzymes break down food into simpler molecules |
| 16. Paper towel absorbs water | P | Capillary action; no chemical change |

✔ Answers:
1. P
2. C
3. P
4. P
5. C
6. C
7. P
8. P
9. C
10. P
11. C
12. C
13. C
14. P
15. C
16. P

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🔹 Part 3: Physical (P) or Chemical (C) Change – Real-Life Examples

| # | Situation | Type (P/C) | Explanation |
|---|---------|------------|-----------|
| 1. An ice cube is placed in the sun. Later there is a puddle of water. Later still the puddle is gone. | P | Melting and evaporation are physical changes; H₂O remains H₂O |
| 2. Two chemicals are mixed together and a gas is produced. | C | Gas production indicates a chemical reaction |
| 3. A bicycle changes color as it rusts. | C | Rusting = oxidation of iron → new substance (iron oxide) |
| 4. A solid is crushed to a powder. | P | Only size/shape changed; no new substance |
| 5. Two substances are mixed and light is produced. | C | Light emission often indicates energy release from a chemical reaction |
| 6. A piece of ice melts and reacts with sodium. | C | Melting is physical, but reaction with sodium is chemical (Na + H₂O → H₂ + NaOH) |
| 7. Mixing salt and pepper. | P | Just mixing; no reaction between them |
| 8. Chocolate syrup is dissolved in milk. | P | Dissolving is physical; mixture can be separated |
| 9. A marshmallow is toasted over a campfire. | C | Browning, charring → chemical changes (combustion, caramelization) |
| 10. A marshmallow is cut in half. | P | Only shape changed; no new substance |

✔ Answers:
1. P
2. C
3. C
4. P
5. C
6. C
7. P
8. P
9. C
10. P

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✔ Final Summary Answers:

#### Properties (P/C):
1. P
2. P
3. C
4. P
5. C
6. C
7. P
8. P
9. C
10. P
11. P
12. P
13. P
14. C

#### Changes (P/C):
1. P
2. C
3. P
4. P
5. C
6. C
7. P
8. P
9. C
10. P
11. C
12. C
13. C
14. P
15. C
16. P

#### Real-Life Examples (P/C):
1. P
2. C
3. C
4. P
5. C
6. C
7. P
8. P
9. C
10. P

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🧠 Key Takeaways:

- Physical changes involve state, shape, size, or phase changes — no new substances.
- Chemical changes involve reactions, color changes, gas formation, odor, heat/light, or new substances.
- Always ask: *"Is a new substance formed?"* If yes → chemical change.

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